The Effect of Urban Green Spaces Reduction on Surface Temperature and Relative Humidity Changes (Case study of Rasht City)

Nowadays, cities are facing with increasing the urban heat island and reduction of the climate comfort Due to the urbanization and the reduction of urban green spaces. This research, therefore, aims to investigate green space reduction and its effects on relative humidity and temperature variability in Rasht, Iran during the period of 1964-2013. To do this, Landsat imagery, daily temperature extremes and relative humidity of the Rasht synoptic station were used. To measure the changes, NDVI, extreme temperature indices and Sen's slope estimator were applied. Results showed that the total green space in Rasht has fallen from about 7,255 hectares to 5,990 hectares and high density green space has dropped from 2855 hectares to 788 hectares. Also, DTR, ID, TN10p indices have been reduced with a 99% confidence. Whereas the indices of TR, TXx as well as TX90p with a confidence of 99%, and maximum relative humidity of Rasht with 95% confidence intervals are increased. Also, trends of the climate parameters are consistent with the green space reduction, and their trends have intensified over three consecutive decades. So that with the population doubling, the city's green space is reduced to about a third of the initial value and the indices such as DTR and FD decreased by about 4 ° C and 35 days, respectively. It seems that the increase of green space is necessary to reduce the effects of the urban heat island and the global warming for sustainable development. It should be taken into consideration in future planning.